Prior art aerosol containers generally include a collapsible bag or pouch disposed therein. The bag or pouch is filled with a fluent material that is dispensed by the container upon actuation of a dispensing valve. A propellant chamber is formed between the bag and the container sidewall. A container end closure is interconnected to the bottom of the side wall and comprises a domed portion with an opening that receives a fill valve. Initially, the bag or pouch is placed in the container and the dispensing valve is attached to a top portion of the container. A propellant is subsequently injected into the container via the fill valve to pressurize the items stored within the bag. For example, a 7 oz. container may contain about 10-12 grams of propellant, such as butane, that is used to pressurize the bag. To inject the propellant, the fill valve is unseated somewhat from the container end closure to provide a space to allow propellant to flow into the chamber and to pressurize the item stored in the bag. The fill valves of the prior art generally include a stem that fits through the aperture in the container end closure, an inner sealing element formed on one side of the stem, and a “bow tie” section formed on the other end of the stem. In addition, opposed longitudinally extending grooves extend from the bow tie section along the side of the stem. During filling, a nozzle presses against the bow tie section of the valve and pushes the valve a sufficient distance inwardly to expose the grooves so that the propellant can flow into the chamber. Additionally, the pressure of the propellant causes the fill valve to flex upward to create a larger opening for the pressurized gas to enter the container. When the nozzle is withdrawn, the pressure in the chamber forces the inner sealing element of the fill valve against the inner surface of the container bottom to seal the container. An example of this type of aerosol container is generally shown in U.S. Pat. No. 5,915,595, which is incorporated by reference in its entirety herein.
A second type of aerosol container utilizes a piston disposed in the container wherein the product to be dispensed is located on an outlet valve side of the piston. The other side of the piston defines a propellant chamber that receives the propellant. The propellant is introduced to the container through a similar fill valve that is fitted into the container end closure in the manner described above.
There are a number of problems associated with aerosol containers that utilize fill valves of the prior art. One significant problem is associated with improper sealing of the fill valve subsequent to filling, which allows propellant to leak from the container. Improper sealing generally refers to a less than ideal engagement between the sealing portion of the fill valve and the aperture of the aerosol container. Propellant leakage associated with improper sealing dramatically reduces product dispensing efficiency, and if a substantial amount of propellant leaks from the container, a “dead” container will result. A “dead” container is one which does not dispense product when the outlet valve is actuated. It will be appreciated by one skilled in the art that the time between a container filling and use may be significant. This period is a function of container packaging, shipping, warehousing and storage. Any loss of propellant, however small, will affect the usefulness of the container. It has been estimated that even a small leak can result in a loss of as much as one gram of propellant per year.
Another related problem occurs during the manufacturing of the fill valve. Generally, fill valves of the prior art are compression molded which has been found to result in poor sealing associated with poor cross linking of the molded material. Cross linking is the formation of chemical links between molecular chains and polymers. Poor cross linking results in poor compression that adversely affects the seal. The result is that even if the fill valve properly seals after filling, propellant may still escape from the container over time due to this poor compression set. In addition, a cryogenic process that is used to remove flash created during compression molding is associated with poor sealing. “Flash”, as used herein, refers to ancillary bits of rubber or other material formed on the finished part during the molding process. During compression molding, flash is created and is later removed by freezing of the product and chipping off the brittle flash. The cryogenic freezing process used to remove the flash may form cracks in the fill valve that potentially become leak paths.
Another problem with fill valves of the prior art is related to indicia identifying the particular mold and mold cavity from which the fill valve was formed. The indicia assists in identifying defective valves. Currently, this indicia is comprised of raised alpha/numeric characters on a surface of the fill valve. The raised characters often influence the movement of the fill valve along conveyor belts associated with the manufacturing process. This haphazard movement of fill valves may result in tipping or sticking to the conveyor belt and require additional manpower to ensure that the fill valves arrive to the assembly station and are properly oriented for insertion into the container end closure.